This invention relates to a method, compositions and kits for the treatment of itching.
Itching is a symptom, commonly associated with dermatitis, caused by various insults in mammals. Insect bites, exposure plants or foods, skin diseases and skin disorders are examples of the kind of insult which can result in itching. Pruritus may also be caused by systemic diseases (such as obstructive bilary disease) or be of unknown origin.
Itching of the skin caused by foods, plants or other insults discussed above is frequently caused by the direct contact of irritants and the skin. However, indirect transfer of irritants, such as by ingestion of foods etc., and transport internally through the body to the skin is also believed to occur and to lead to itching. In the art, compounds which induce itching, dermatitis, or both can be referred to as allergens or allergenic compounds, sensitizing or sensitizer compounds, elicitor compounds, irritants or other similar names. In this description, no distinction is made between any of these names, but for convenience they are generally referred to simply as "irritants."
Plant irritants are exemplary of the irritants which come into contact with the skin and lead to itching. For example, itching is commonly associated with contact dermatitis induced by irritants present in plants of the Anacardiaceae and Ginkgoaceae families. Included among these plants are the Toxicodendrons, e.g., poison ivy (T. radicans), Eastern poison oak, (T. quercifolium), poison sumac (T. vernix), and Western poison oak (T. diversilobum). Also included are manzanillo (Rhus striata), Japanese lac (R. verniciflua), Mango tree (Mangifera indica), India ink tree, (Semicarpus anacardum), ginko tree (Ginko biloba L.), and the cashew tree (Anacardium occidentale).
One such group of plant-borne irritants is a mixture of alkyl-catechols known as the urushiols. Urushiols are present in, e.g., poison ivy and Japanese lac, and are known to induce the contact dermatitis commonly known as "poison ivy" rash. One to two million people are said to be afflicted with varying degrees of poison ivy rash each year. It has been estimated that as many as 150,000 working days are lost annually to urushiol induced contact dermatitis. (Vietmeyer, N. Smithsonian Vol. 16, no. 5, August 1985).
The mechanism of action of urushiols in inducing contact dermatitis has been described in the literature. (See, e.g., Lepoittevin, J-P. and Benezra, C. Allergic contact dermatitis caused by naturally occurring quinones. Pharm. Weekbl Sci! (Netherlands) Jun. 21, 1991. 13(3):119-122). It is believed that the mechanism of action of the urushiols may be general to many irritants that lead to itching. Briefly, the process leading to urushiol-induced contact dermatitis, or poison ivy rash, is reported to be as follows. Urushiols are transmitted from the plant to the skin and are oxidized in vivo to ortho-quinones. The ortho-quinones are thought to interact with proteins and form quinone-protein conjugates which act as the actual antigens. Next, the conjugates are reported to be presented to inexperienced T-lymphocytes by epidermal macrophages. The exposed lymphocytes can develop into immunologically competent lymphocytes which are capable of reacting to subsequent exposure to the urushiols. At this point a mammal is said to be sensitized to the urushiols. The subsequent exposure of these competent lymphocytes to urushiol (ortho-quinone)-protein conjugates is thought to lead to the release of lymphokines and the manifestation of urushiol induced contact dermatitis--the poison ivy rash.
Poison ivy rash starts with a reddening of the skin and itching. The itching intensifies with time and watery blisters appear. The itching typically causes afflicted mammals to scratch the affected area. This can delay healing and can spread urushiols to a wider area of the skin or other parts of the body.
The widespread occurrence of poison ivy induced dermatitis has led to the proposal of many treatments to prevent or alleviate the symptoms of the poison ivy rash. Methods reported to prevent the rash include the use of desensitizing materials, urushiol absorbing materials, and forming protective layers on the skin to block irritants. Reportedly useful methods for alleviating symptoms include applying plant extracts, corticosteroids, and enzymes including catechol oxygenase or p-diphenol oxidase, washing irritants from the skin with polyglycol ethers, thymopentin therapy and the use of topical anesthetics. (Examples of reportedly useful methods of treatment to prevent or alleviate symptoms of contact dermatitis can be found in U.S. Pat. Nos. 5,086,075; 5,049,580; 5,036,050; 5,017,361; 5,011,689; 4,861,584; 4,738,956; 4,344,965; 4,428,965; 4,259,318; 4,199,575; 4,160,819; 4,144,319; 4,141,966; 4,137,301; 4,112,067; 4,002,737 and 3,974,281; Canadian Patent No. 1032473; and European Patent No. 0 311 963 A1, all of which are incorporated herein by reference.)
In addition, there are numerous purportedly effective ethnobotanical treatments for alleviating itching, including the itching associated with poison ivy. However, the use of plant material or crude plant extracts in therapeutic methods, compositions and kits can have undesirable drawbacks. These include the presence in the final composition of unknown or undesirable irritants that can exacerbate itching, dermatitis, or both. Compositions can also vary widely in components and component concentrations depending on factors such as method of preparation or plant growth conditions, e.g., soil type, nutrient supply, season, water supply, etc. Other drawbacks and dangers of applying plant materials to dermatitis include the potential presence of excess bulk; irritating bits of leaf, stem or root; soil; insect parts and infectious microorganisms.
One such ethnobotanical cure purported that jewelweed was an effective plant in the treatment of itching associated with poison ivy rash. However, publications have dismissed the value of treatments using this plant (Zink, B. J. et al. 1991. Journal of Wilderness Medicine, Vol. 2:178-182).